Document scanners convert a visible image on a document or photograph, or a image in a transparent medium, into an electronic form suitable for copying, storing or processing by a computer. A document scanner may be a separate device or a document scanner may be a part of a copier, part of a facsimile machine, or part of a multipurpose device. Reflective document scanners typically have a controlled source of light which is reflected off the surface of a document, through an optics system, and onto an array of photosensitive devices. The photosensitive devices convert received light intensity into an electronic signal. Transparency scanners pass light through a transparent image, for example a photographic positive slide, through an optics system, and then onto an array of photosensitive devices.
Reflective document scanners may be adapted to scan transparent images by providing a separate light source to back-light the image. U.S. Pat. No. 5,463,217 (Sobol et al.), which is incorporated herein for all that it teaches and describes, describes a completely passive adapter for scanning transparent images in a reflective scanner without requiring a separate light source for back lighting. A light source in the reflective scanner provides light which passes outside the area of the transparent image. The adapter captures light which passes outside the area of the transparent image and reflects the light through the transparent image. The reflected light re-enters the scanner along the optical path required by scanner internal optics. The various embodiments described in Sobol et al. are suitable for a fixed scanner optical path. However, when a new scanner is developed, the angle of the adapter mirrors may need to change to accommodate a different optical path within the new scanner. There is a need for an adjustable adapter that can be adjusted to different optical paths in different scanners, thereby permitting a single adapter to be used with multiple scanner designs. In addition, for some scanners, the lamp leads the scan line during scanning movement, and for other scanners, the lamp lags the scan line during scanning movement. There is a need to ensure that for either case, when the scan line is within the image to be captured, then the lamp is within the light capture area for the adapter.